Fix WM input limitations on secondary displays (2/4)

- Change setInputWindow of InputManagerService to carry displayId,
  so InputWindowHandle can be updated by each DisplayContent.
- If focus window exist in current display, we need to reset it to nullptr
  in the intermediate state before the new focus set,
  to prevent it will access the released info.
- use INDENT2 for dump window under display, and likewise below.
- Some test cases for setInputWindow

Bug: 111363643
Test: atest WindowManagerSmokeTest ActivityManagerMultiDisplayTests
Test: atest com.android.server.wm.DisplayContentTests
Test: atest libinput_tests inputflinger_tests
Change-Id: I658eacb62433e3e70d6c58b47215291078cc2076